<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <select id="province" onchange="selectCity(this)">
      <option value="0">‐请选择‐</option>
      <option value="1">陕西</option>
      <option value="2">四川</option>
      <option value="3">甘肃</option>
    </select>
    <select id="city">
      <option value="">‐‐请选择市‐‐</option>
    </select>

    <script src="cascade.js"></script>
  </body>
</html>
